This invention relates to optical fiber modules for installation in a distribution frame.
Optical fiber cross-connect distribution frames serve the function of coupling incoming fiber optic cables to customer equipment. Each shelf of the frame includes a plurality of modules, each module comprising a set of optical fiber connectors on a front panel, and means for receiving the fibers from the incoming cable for connection to the connectors on the front panel. These modules should be capable of retrofitting into existing cross-connect frames, such as AT&T's LGX.RTM. Distribution System, and also must be easily removed and reinstalled for the purposes of maintenance and repair. Consequently, sufficient cable slack should be provided in the shelf when the module is installed so that a craftsperson can work on the module at some distance away from the shelf when it is removed.
Optical fiber cable coming into a standard cross-connect frame usually has internal reinforcement members and a fairly thick protective sheath (i.e., of the order of 0.15 to 0.36 inches in diameter) in order to protect the fiber ribbons in the cable. The cable, therefore, tends to be fairly stiff. Further, the cable usually requires a bend radius of at least 3 inches to ensure that the fibers are not damaged. It is, therefore, difficult to bend the cable in such a way as to provide the necessary slack in the area provided in the shelf while maintaining the minimum bend radius.
The usual approach to this problem is to cut the cable sheathing and reinforcement member so that only the fiber ribbons enter the module. Sometimes, an intermediate tubing can be provided around the fibers which enter the module (see, e.g., U.S. Pat. No. 5,071,211 issued to Debortoli, et al.).
While these approaches may be adequate, they do not provide the full protection of the fibers afforded by the cable sheathing and reinforcement member.
Consequently, it is an object of the invention to provide a module which permits direct entry of an optical fiber cable, including its sheathing, while providing the needed cable slack when the module is installed in a distribution shelf.